JPH0773132B2 - Semiconductor light emitting device and method of manufacturing the same - Google Patents

Description

The present invention relates to a semiconductor light emitting device and a method for manufacturing the same.

[Prior Art] In a conventional semiconductor light emitting device having a buried hetero structure, as shown in FIG.
_It has a structure surrounded by a buried layer 6 made of _1-x Al _x As _{x (X} to _0.3) . The structure of this semiconductor light emitting device is described in the following fifth
The manufacturing process will be described with reference to the drawings. As shown in FIG. 5 (A), n-type Ga _0.7 Al _{0.3 is formed} on the n-type GaAs substrate 1.
The As clad layer 2, the p-type GaAs active layer 3, the p-type Ga _0.7 Al _0.3 As clad layer 4, and the p-type GaAs cap layer 5 are successively and successively grown. At this time, as the crystal growth method, a liquid phase epitaxial growth method (LPE method), a molecular beam epitaxial growth method (MBE method), a metal organic chemical vapor deposition method (MO-CVD method), or the like is used.

Next, as shown in FIG. 5 (B), the p-type GaAs cap layer 5 is formed.
A mask 9 made of a SiO ₂ film having a predetermined pattern is placed on the above,
Using this as a mask, n-type Ga _0.7 Al _0.3 As clad layer 2, p-type G
aAs active layer 3, p-type Ga _0.7 Al _0.3 As clad layer 4 and p-type GaAs
The cap layer 5 is subjected to mesa etching to reach the GaAs substrate 1.

Next, as shown in FIG. 5 (C), the Ga _0.7 Al _0.3 As embedded layer 6 is formed so as to completely cover the p-type GaAs active layer 3 on the main surface of the GaAs substrate 1 exposed by mesa etching. Are formed by a liquid phase epitaxial growth method to obtain a semiconductor light emitting device.
The liquid phase epitaxial growth method is used here to prevent crystal growth on the cap layer 5 by using the mask 9 as a dielectric thin film. In addition, the injection current is applied to the active layer 3
In order to reduce the operating current of the light-emitting device by concentrating only on the portion of (7), the electric resistance of the Ga _0.7 Al _0.3 As embedded layer 6 is made high, or as shown in FIG. Include layer 6 '
From the GaAs substrate 1, p-type Ga _0.7 Al _0.3 As layer 6′a and n-type Ga _{0.7
For example, 0.7} Al _0.3 As layers 6'b are sequentially laminated to form an npn structure.

In FIG. 4, 7 is a negative electrode vapor deposition film formed on the back surface side of the GaAs substrate 1, and 8 is a positive electrode vapor deposition film formed on the main surface sides of the embedding layer 6 and the cap layer 5. It is a film.

[Problems to be Solved by the Invention] Such a conventional semiconductor light emitting device has the following problems. Since the side wall of the active layer 3 is exposed to the air during the mesa etching, the crystal characteristics, the accumulation of impurities and the like generated at the end of the active layer and the vicinity thereof deteriorate the device characteristics. That is, the non-radiative recombination of the injected carriers involved in the interface states associated with crystal defects and the like reduces the light emission efficiency, and further, the element deterioration due to the multiplication of crystal defects significantly impairs the long-term reliability of the element. It was

In addition, the conventional method for manufacturing a semiconductor light emitting device has the following problems. That is, the crystal growth is required twice, which complicates the manufacturing process. Furthermore, in recent years, considering the film thickness controllability and film thickness uniformity, MO CVD (Me) has been adopted from the viewpoint of mass production as a crystal growth method that replaces the LPE (Liquid phase epitaxy) method.
tal Organic Chemical Vapor Peposition) method is drawing attention, but in these vapor phase growth methods, selective epitaxy technology as shown in FIGS. 5 (C) and 5 (D) has not been established. There is a problem that the semiconductor light emitting device as shown in (3) cannot be easily mass-produced.

The present invention has been made in view of the above points, and it is possible to form an embedded layer in which the active layer is buried by embedding the active layer by a series of crystal growth processes at one time, without the need for etching the active layer. The present invention has developed a semiconductor light emitting device capable of exhibiting high reliability for a long period of time and a manufacturing method thereof.

[Means for Solving the Problems] The present invention provides a mesa stripe protruding in a stripe shape substantially parallel to a <110> direction or a crystal axis direction equivalent to the main surface of a semiconductor substrate, and a mesa stripe on the mesa stripe. A double heterostructure including an active layer that is laminated and has {} B planes on both sides, and the double heterostructure is formed on the exposed main surface of the semiconductor substrate except the mesa stripe so as to be embedded in the active layer. A semiconductor light emitting device comprising: a semiconductor layer having a refractive index smaller than that of the layer and a bandgap larger than that of the layer.

In the semiconductor light emitting device according to the present invention, it is preferable that the double hetero structure has an isosceles triangular cross section in which a double cross is a {} B plane.

In addition, the present invention comprises a step of forming a mesa stripe projecting in a stripe shape on the main surface of a semiconductor substrate in a direction substantially parallel to the <110> direction or a crystal axis direction equivalent to the <110> direction. A step of stacking a double hetero structure including an active layer which is a B-plane, and having a refractive index smaller than that of the active layer by embedding the double hetero structure on the exposed main surface of the semiconductor substrate excluding the mesa stripe. A method of manufacturing a semiconductor light emitting device, comprising: a crystal growth step of the double hetero structure and a step of forming a semiconductor layer having a large bandgap by a series of crystal growth steps.

Here, the important points of the semiconductor light emitting device and the manufacturing method thereof according to the present invention are as follows. That is, as shown in FIG. 3, the mesa stripes 21 protruding linearly in the <110> direction of the semiconductor substrate 20 or in the crystal axis direction which is crystallographically equivalent thereto.
When the crystal growth is performed on the semiconductor substrate 20 by MO-CVD method or the like, the growth layer 22 is formed on the main surface of the semiconductor substrate 20 on both sides of the mesa stripe 21. The growth layer 22 is separated on the surface of the mesa stripe 21 {}
A stripe structure 23 having an isosceles triangular cross section, which is limited by a surface corresponding to the surface (B surface), is formed. Furthermore,
It has been experimentally confirmed that the crystal growth rate on the {} plane (B plane) is extremely smaller than the crystal growth rate on other planes. The present invention was created based on such technical matters.

[Operation] According to the semiconductor light emitting device of the present invention, since the portion of the mesa stripe structure 23 including the active layer is formed and embedded by one continuous crystal growth, the active layer edge portion is formed. And no accumulation of crystal defects and impurities in the vicinity,
It is possible to prevent non-radiative recombination of the injected carriers associated with the interface states associated with crystal defects and to obtain high luminous efficiency. In addition, it can exhibit high reliability for a long period of time.

Further, according to the method of the present invention, the portion of the mesa stripe structure 23 can be formed without being necessary for the etching process.
Moreover, the mesa stripe structure 23 and its embedded layer can be formed by a series of one-time crystal growth processes. Further, the mesa stripe structure 23 can be formed by a crystal growth method such as MO-CVD method. Therefore, mass productivity can be improved. As a result, the semiconductor light emitting device can be easily obtained with a high yield.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. The description of the structure of the semiconductor light emitting device of one embodiment of the present invention will be replaced with the description of the method of the present invention in the order of the steps described below.

First, as shown in FIG. 1A, for example, an n-type GaAs substrate 30
On the (100) plane of the stripes parallel to the <110> direction
The SiO ₂ film 31 is formed by the photolithography method.

Next, as shown in FIG. 1B, the GaAs substrate 30 is subjected to selective etching using the SiO ₂ film 31 as a mask to form a mesa stripe 32 protruding in a stripe shape on the main surface of the GaAs substrate 30.

Next, as shown in FIG. 1C, after the SiO ₂ film 31 is removed, a crystal growth process is performed on the GaAs substrate 30 including the mesa stripes 32 by the MO-CVD method. The n-type Ga _0.7 Al _0.3 As clad layer is formed on the mesa stripe 32 by this crystal growth process.
A striped double heterostructure 36 is formed by sequentially stacking 33, the non-doped GaAs active layer 34, and the p-type Ga _0.7 Al _0.3 As cladding layer 35. Striped double heterostructure 36
The crystal growth is extremely slow because the crystal growth is limited by the {} plane (B plane), so that the cross section has an isosceles triangular shape. Also, a striped double heterostructure
At the same time as the formation of 36, the n-type Ga _0.7 Al _0.3 As layer 33 ′, on the main surface ((100) surface) of the GaAs substrate 30 sandwiching the mesa stripe 32,
Non-doped GaAs layer 34 ', p-type Ga _0.7 Al _0.3 As clad layer 35'
Are sequentially stacked. Here, as the p-type Ga _0.7 Al _0.3 As cladding layer 35 'does not contact the p-type Ga _0.7 Al _0.3 As cladding layer 35 on the mesa stripe 32, advance the height of the mesa stripe 32 (t ₁₎ and the n-type Ga _0.7 Al _0.3 As The thickness of the cladding layer 33 and the like is set to a predetermined value. Each layer 33… 35,3
The thickness control of 3 '... 35' can be extremely easily performed by the MO-CVD method.

Next, as shown in FIG. 1 (D), the crystal growth treatment by the MO-CVD method described above is continuously performed using the specified reaction gas, and the striped double hetero structure 36 of the non-doped GaAs is subjected to the above-mentioned process. Non-doped Ga _0.7 A that completely fills the active layer 34
A _0.3 As buried layer 37 is laminated on the p-type Ga _0.7 Al _0.3 As cladding layer 35. Next, the p-type cap layer 38 is formed on the non-doped Ga _0.7 Al _0.3 As embedded layer 37.

Then, as shown in FIG. 1E, the p-type electrode 39 is formed on the p-type cap layer 38 by vapor deposition, and the n-type electrode 40 is formed on the back surface of the GaAs substrate 30 to form the semiconductor light emitting device 45. To get

According to the semiconductor light emitting device 45 having such a structure, the double heterostructure 36 including the active layer having {} B planes on both sides is formed on the mesa stripe 32 by one continuous crystal growth process. Since it is a non-doped active layer
Crystal defects and impurities do not accumulate at the edge of 34 and its vicinity, and excellent composition characteristics can be exhibited for a long time.

According to the method for manufacturing a semiconductor light emitting device described above, an etching process is not required when forming the stripe-shaped double hetero structure 36, and furthermore, the stripe structure 36 is formed and embedded by a series of single crystal growth processes. Since the layer 37 and the cap layer 38 can be formed and the crystal growth process by the MO-CVD method can be adopted, the semiconductor light emitting device 45 capable of exhibiting excellent element characteristics for a long time can be easily obtained with a high yield. be able to.

In the semiconductor light emitting device according to the embodiment shown in FIG. 1 described above, the n-type clad layer 33, the active layer 34, and the p-type clad layer 34 are sequentially formed on the mesa stripe 32, and a mesa stripe formed by stacking these layers is formed. The structure 36 has a cross section of a substantially isosceles triangle. When a buried layer (current blocking layer) 37 is deposited on the structure having the mesa stripe structure 36, the growth proceeds along the side surface of the mesa stripe structure 36, and the top of the mesa stripe structure 36 is formed. Never grow to.

On the other hand, when the mesa stripe structure 36 is not an isosceles triangle but a trapezoidal shape, growth easily occurs at the apex corresponding to the upper side of the trapezoid, which hinders current flow to the active layer. In order to prevent this, Zn may be diffused into the substrate in advance before the buried layer (current blocking layer) 37 is deposited, but this is not preferable because it leads to an increase in the number of steps.

Fig. 2 shows the non-doped Ga _0.7 Al _0.3 As buried layer 37 with p-type Ga.
₇ shows another embodiment in which an n-type Ga _0.7 Al _0.3 As embedded layer 47 is laminated on a _0.7 Al _0.3 As embedded layer 46 to form a double structure. Here, the p-type Ga _0.7 Al _0.3 As layer 35 'and the p-type Ga _0.7 Al _0.3 As buried layer
46 does not necessarily have the same composition and the same carrier concentration. The portions other than the buried layers 46 and 47 have the same structure as that of the above-mentioned embodiment.

In the embodiment, the n-type GaAs substrate 30 is used, but it goes without saying that a p-type substrate may be used.

In addition to the non-doped GaAs layer, the active layer 34 includes p-type GaAs and n-type
Of course, it may be formed of a GaAs layer. Furthermore, the active layer may have a quantum well structure.

In addition to the MO-CVD method, the crystal growth process is performed by VPE (Vapor
The Phase Epitaxy method or MBE (Molecular Beam Epitaxy) method may be adopted.

Further, in the embodiment, the GaAs / GaAlAs based semiconductor light emitting device has been described, but it is needless to say that the present invention can be applied to an InP / InGaAsP based semiconductor light emitting device.

[Effects of the Invention] As described above, according to the semiconductor light emitting device and the method for manufacturing the same according to the present invention, it is possible to embed the active layer by performing a series of crystal growth processes at once without the need for etching the active layer portion. It is possible to form up to the embedded layer, and it is possible to easily obtain a semiconductor light emitting device that exhibits high reliability for a long period of time. Further, according to the method of the present invention, crystal growth treatment such as MO-CVD method can be adopted, so that the above-mentioned semiconductor light emitting device can be mass-produced with high yield.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a semiconductor light emitting device of an embodiment of the present invention in the order of steps, FIG. 2 is an explanatory view showing a schematic configuration of another embodiment of the semiconductor light emitting device according to the present invention, and FIG. FIG. 4 is an explanatory diagram showing an important configuration of the present invention, FIG. 4 is an explanatory diagram showing a schematic configuration of a conventional semiconductor light emitting device, and FIG. It is a figure. 20 ... Semiconductor substrate, 21 ... Mesa stripe, 22 ... Growth layer, 23 ... Mesa stripe structure, 30 ... GaAs substrate, 31 ...
… SiO ₂ film, 32 …… Mesa stripe, 33,33 ′ …… n-type Ga
_0.7 Al _0.3 As clad layer, 34 ... Non-doped GaAs active layer,
35,35 '…… p-type Ga _0.7 Al _0.3 As cladding layer, 36 …… Striped double heterostructure, 37 …… Undoped Ga _0.7 A
l _0.3 As Buried layer, 38 …… Cap layer, 39 …… P-type electrode, 40
... n-type electrode, 45 ... semiconductor light-emitting device, 46 ... P-type Ga
_0.7 Al _0.3 As buried layer, 47 ... n-type Ga _0.7 Al _0.3 As buried layer.

Claims (4)

[Claims] 1. A mesa stripe projecting in a streak shape on a main surface of a semiconductor substrate in a direction substantially parallel to a <110> direction or a crystal axis direction equivalent to the <110> direction, and stacked on the mesa stripe. A double heterostructure including an active layer which is a surface, and a double heterostructure formed so as to be embedded on the exposed main surface of the semiconductor substrate excluding the mesa stripe, and having a smaller refractive index than the active layer, and And a semiconductor layer having a large forbidden band width. 2. The double hetero structure has a double-sided surface {
The semiconductor light emitting device according to claim 1, which has an isosceles triangular cross-section that is a B plane. 3. A step of forming a mesa stripe projecting in a streak shape substantially parallel to a <110> direction or a crystal axis direction equivalent to the <110> direction on a main surface of a semiconductor substrate, and both side surfaces on the mesa stripe are {}. Stacking a double heterostructure including an active layer which is a B-plane, and having a refractive index smaller than that of the active layer by embedding the double heterostructure on the exposed main surface of the semiconductor substrate except the mesa stripe, A method of manufacturing a semiconductor light emitting device, comprising: a crystal growth step of the double hetero structure and a step of forming a semiconductor layer having a large band gap by a series of crystal growth steps. 4. The method for manufacturing a semiconductor light emitting device according to claim 3, wherein the double hetero structure and the crystal growth method of the semiconductor layer are MO-CVD methods.